A magnetic shield is used for electronic drawing equipment using an electron beam and an instrument for measuring a biomagnetic field which measures a weak magnetic field generated from a living body. In general, a magnetically shielded room is constructed as a closed room formed by fastening plates of permalloy of an Fe-Ni alloy containing 35 to 80% Ni with high permeability with bolts with no space to a box type constructional frame of aluminum or stainless. To increase the shielding factor, the plates of permalloy are multilayered. To perform, not only magnetic shield, but also electric wave shield, a wall made of an aluminum plate having a thickness of about 1 to 10 mm is provided between the permalloy layers. The magnetic shield using the permalloy requires a number of parts and heat treatment after processing.
Instead of the permalloy, there is known a magnetic shield using a magnetic shielding sheet obtained by laminating the thin film of a high-permeability soft magnetic amorphous alloy onto a polymer film (see Patent Documents 1 and 2). In the prior art, a wall is made of a material constructed of a nonmagnetic substance to laminate the magnetic shielding sheet onto the wall for constructing a magnetically shielding room or a cylindrical magnetic shield.
There is known a magnetic shielding container in which a number of annular high-permeability magnetic substances of the same type as an inner wall of the container are laminated inside the magnetic shielding container constructed of superconductors and having tubular opening parts (see Patent Document 3).
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-077890
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-136492
[Patent Document 3]
Japanese Patent Application Laid-Open No. Hei 7-226598